Line games are among the most popular games in the gaming industry. The diversity of themes, schemes and bonuses they offer is probably the key reason for their popularity. They are entertaining and easy to play; even though the player does not know all the rules, he still can enjoy the game and his chances of winning are not diminished.
One of the features already popular in line games is the meter; by gathering symbols or combination of symbols, the meter triggers second-screen bonuses, free spins, special prizes, or any other feature. Usually, the meter consists in a value increasing throughout the game with the accumulation of a symbol or event, and is displayed as a number, a gathering of objects on a screen or as a graphical representation, like a thermometer. When the meter reaches a target value, a feature is automatically triggered. An example of a game using a meter having a graphical representation is IGT's “Wild Cherry Pie” game; the cherries appearing on the reels are gathered in a pie drawing displayed over these reels. When a section of the pie is full of cherries, an instant bonus prize is awarded to the player. Upon completion of the pie, the player is taken to a second screen bonus. This meter feature has no influence on the primary game payout or on the probability of winning in said primary game.
Another feature is to modify some symbol characteristics, such as its appearance, properties, prize value, etc. Manufacturers have used this feature in many ways. U.S. Pat. No. 6,059,642 describes a game wherein, upon occurrence of a winning outcome, a second random number generator determines a color for the background of each symbol participating to the winning outcome. If the symbols participating to the winning outcome are all of the same color, a bigger prize is awarded to the player. Another way to use the symbol modification feature is described in U.S. patent application Ser. No. 20020052233: the occurrence of a wild symbol at a predetermined position triggers the modification of the symbols displayed on the same reel. These modifications are linked to the current spin or play only and do not have any influence on the payout or the probability of winning of subsequent spins or plays.
Improvements in such line games are desired to keep players interested.